Oxazolidinone antibiotics are a relatively new class of antibacterial agents with activity against a broad spectrum of gram-positive pathogens. The first member of this new class to be commercialized, linezolid, was approved in 2000. Since that time the development of linezolid resistant organisms has prompted efforts to discover more effective members of the oxazolidinone class. A new family of biaryl oxazolidinone antibacterials with activity against both linezolid-susceptible and -resistant Gram-positive bacteria, as well as certain Gram-negative bacteria has been reported (see Bioorganic & Medicinal Chemistry Letters, 2008, 18, 6175-6178, and PCT Patent Publication WO 2005/019211). Among the known biaryloxazolidinones is N-[3-(2-fluoro-4′-{[(1H-[1,2,3]triazol-4-ylmethyl)-amino]-methyl}-biphenyl-4-yl)-2-oxo-oxazolidin-5-ylmethyl]-acetamide, more commonly known as radezolid (RX-1741), currently being developed for multi-drug-resistant infections.
Although a monohydrochloride salt of radezolid was disclosed in PCT Patent Publication WO 2006/133397, there is a continuing need for new salts and polymorphs thereof having improved properties such as solubility to optimize bioavailability on therapeutic administration.